Sunflower (Helianthus annuus L.) now ranks second among all oilseed crops in the world as a source of edible vegetable oil. Sunflower is used as human food, livestock feed, and as raw material in industry. The food uses of sunflower include snack foods, cooking mediums and salad oils. Whole achenes are an important component of bird and other small animal feeds. Sunflower silage has utility as a livestock feed.
Sunflower oil is also used in the manufacture of margarine, soap, pharmaceuticals, shortening, lubricants and as a source for biodiesel fuels. Sunflower hulls can be pressed into logs for use in the fireplace and cooking stoves.
Sunflower hybrids can be classified into two broad categories: Confection (non-oil) and oil types. Confection sunflower seeds may be further divided into three classes: in-shell, kernel and birdseed. In-shell seed refers to larger sunflower seeds which may be roasted, salted and packaged for human consumption. Kernel seed refers to medium sized seeds which may be dehulled and also packaged for human consumption. Smaller seed may be sold in birdseed markets. Oil-type sunflower seed is richer in oil and therefore better suited to the production of sunflower oil and is used to produce ingredients for animal feed. Oil sunflower hybrids may be further divided into three classes: linoleic (regular oil type), NuSun (mid-oleic), and high oleic. A third category of sunflower seed referred to as hybrid seed has attributes of both confection and oil type sunflowers.
The goal of a sunflower breeder is to improve a sunflower plant's performance and therefore, its economic value by combining various desirable traits into a single plant. Improved performance is manifested in many ways. Higher yields of sunflower plants contribute to a more abundant food supply, a more profitable agriculture and a lower cost of food products for the consumer. Improved quality makes sunflower kernels more nutritious. Improved plant health increases the yield and quality of the plant and reduces the need for application of protective chemicals. Adapting sunflower plants to a wider range of production areas achieves improved yield and vegetative growth. Improved plant uniformity enhances the farmer's ability to mechanically harvest sunflower.
Sunflower is a dicot plant with perfect flowers, i.e., sunflower has male, pollen-producing organs and separate female, pollen receiving organs on the same flower. The cultivated sunflower inflorescence, or flower head is composed of about 700 to 3000 individual flowers attached to a common base called a receptacle. Ligulate ray flowers are present around the circumference of the receptacle but do not have stamens or pistils. The remaining flowers are disk flowers, which are arranged in arcs radiating from the center of the head. The disk flower is complete and consists of a basal inferior ovary, two pappus scales (modified sepals), a tubular corolla of five petals that are united, except for the tips, five anthers united to form a tube with separate filaments attached to the base of the corolla tube, and one style terminating in a divided stigma curled outward to the anther tube. Each floret matures over several days. At maturity each floret consists of separate male, longated pollen-shedding anther filaments and a female elongated pollen-receptive stigma.
Because sunflower has both male and female organs on the same flower, sunflower breeding techniques take advantage of the plant's ability to be bred by both self-pollination and cross-pollination. Self-pollination occurs when pollen from the male organ is transferred to a female organ on the same flower on the same plant. Self-incompatability is a form of infertility caused by the failure of sunflower plants with normal pollen and ovules to set seed due to some physiological hindrance that prevents fertilization. Self-incompatability restricts self-pollination and inbreeding and fosters cross-pollination. Cross-pollination occurs when pollen from the male organ on the flower of one plant is transferred to a female organ on the flower on a different plant.
A plant is sib-pollinated (a type of cross-pollination) when individuals within the same family or line are used for pollination (i.e. pollen from a family member plant is transferred to the stigmas of another family member plant). Self-pollination and sib-pollination techniques are traditional forms of inbreeding used to develop new inbred sunflower lines, but other techniques exist to accomplish inbreeding. New inbred sunflower lines are developed by inbreeding heterozygous plants and practicing selection for superior plants for several generations until substantially homozygous plants are obtained. During the inbreeding process with sunflower, the vigor of the lines decreases and after a sufficient amount of inbreeding, additional inbreeding merely serves to increase seed of the developed inbred. Inbred sunflower lines are typically developed for use in the production of hybrid sunflower lines.
Natural, or open pollination, occurs in sunflower when bees or other insects transfer pollen from the anthers to the elongated stigmas that protrude from the florets and may include both self- and cross-pollination. Such pollination is accomplished almost entirely by the bees or other pollinating insects and accordingly, interplant transfer of pollen by the wind is of little importance. Vigor is restored when two different inbred lines are cross-pollinated to produce the first generation (F1) progeny. A cross between two defined homozygous inbred sunflower plants always produces a uniform population of heterozygous hybrid sunflower plants and such hybrid sunflower plants are capable of being generated indefinitely from the corresponding inbred sunflower seed supply.
When two different, unrelated inbred sunflower parent plants are crossed to produce an F1 hybrid, one inbred parent is designated as the male, or pollen parent, and the other inbred parent is designated as the female, or seed parent. Because sunflower plants are capable of self-pollination, hybrid seed production requires elimination of or inactivation of pollen produced by the female parent to render the female parent plant male sterile. This serves to prevent the inbred sunflower plant designated as the female from self-pollinating. Different options exist for controlling male fertility in sunflower plants such as physical emasculation, genetic male sterility, cytoplasmic male sterility and application of gametocides. Incomplete removal of male parent plants from a hybrid seed production field before harvest provides the potential for unwanted production of self-pollinated or sib-pollinated seed which may be unintentionally harvested and packaged with hybrid seed.
The development of new inbred sunflower plants and hybrid sunflower plants is a slow, costly interrelated process that requires the expertise of breeders and many other specialists. The development of new hybrid sunflower varieties in a sunflower plant breeding program involves numerous steps, including: (1) selection of parent sunflower plants (germplasm) for initial breeding crosses; (2) inbreeding of the selected plants from the breeding crosses for several generations to produce a series of inbred lines, which individually breed true and are highly uniform; and, (3) crossing a selected inbred line with an unrelated line to produce the F1 hybrid progeny having restored vigor.
Inbred sunflower plants and other sources of sunflower germplasm are the foundation material for all sunflower breeding programs. Despite the existence and availability of numerous inbred sunflower lines and other source germplasm, a continuing need still exists for the development of improved germplasm because existing inbred parent sunflower lines lose their commercial competitiveness over time. The present invention addresses this need by providing a novel inbred parent sunflower line designated CN1703 that contributes improved seed yield and oil yield per acre to hybrids relative to other similar hybrids in the same maturity groups. To protect and to enhance yield production, trait technologies and seed treatment options provide additional crop plan flexibility and cost effective control against insects, weeds and diseases, thereby further enhancing the potential of hybrids with CN1703 as a parent.